Harmonic drive camshaft phaser using oil for lubrication

Abstract

A camshaft phaser includes a housing with an array of internal splines formed within a bore. A harmonic gear drive unit is disposed within the housing and includes a circular spline and a dynamic spline, a flexspline disposed within the circular spline and the dynamic spline, a wave generator disposed within the flexspline, and a rotational actuator connectable to the wave generator. One of the circular spline and the dynamic spline is fixed to the housing. A hub is rotatably disposed within the housing and attachable to the camshaft and fixed to the other of the circular spline and the dynamic spline. An oil passage is provided for receiving oil from an internal combustion engine for lubricating the harmonic gear drive unit.

We claim: 
     
       1. A camshaft phaser for controllably varying the phase relationship between a crankshaft and a camshaft in an internal combustion engine, said camshaft phaser comprising:
 a housing having a bore with a longitudinal axis; 
 a harmonic gear drive unit disposed within said housing, said harmonic gear drive unit comprising a circular spline and an axially adjacent dynamic spline, a flexspline disposed within said circular spline and said dynamic spline, a wave generator disposed within said flexspline, and a rotational actuator connectable to said wave generator such that rotation of said wave generator causes relative rotation between said circular spline and said dynamic spline, wherein one of said circular spline and said dynamic spline is fixed to said housing in order to prevent relative rotation therebetween; 
 a hub rotatably disposed within said housing axially adjacent to said harmonic gear drive unit and attachable to said camshaft and fixed to the other of said circular spline and said dynamic spline in order to prevent relative rotation therebetween; and 
 a harmonic drive oil passage through said hub for receiving oil, in use, from said internal combustion engine, said harmonic drive oil passage being in fluid communication with said harmonic gear drive unit for supplying said oil thereto. 
 
     
     
       2. A camshaft phaser as in  claim 1  wherein a bearing surface interface is formed between said housing and said hub, and wherein a bearing surface oil passage is in fluid communication with said bearing surface interface for supplying said oil thereto. 
     
     
       3. A camshaft phaser as in  claim 2  wherein said harmonic drive oil passage is in fluid communication with said bearing surface oil passage for receiving said oil therefrom. 
     
     
       4. A camshaft phaser as in  claim 3  wherein said harmonic drive oil passage includes an orifice for restricting the flow of oil therethrough. 
     
     
       5. A camshaft phaser as in  claim 4  wherein said orifice is formed in a plug that is inserted within said harmonic drive oil passage. 
     
     
       6. A camshaft phaser as in  claim 2  wherein said bearing surface oil passage is formed radially through said hub. 
     
     
       7. A camshaft phaser as in  claim 6  wherein said harmonic drive oil passage extends from said bearing surface oil passage in a direction substantially parallel to said longitudinal axis. 
     
     
       8. A camshaft phaser as in  claim 6  further comprising:
 an axial bore extending coaxially through said hub; 
 a camshaft phaser attachment bolt extending coaxially through said axial bore and being threadably engageable with said camshaft for attaching said camshaft phaser to said camshaft, said camshaft phaser attachment bolt defining an annular oil chamber with said axial bore; and 
 an oil supply passage through said hub for supplying said oil from said internal combustion engine to said annular oil chamber; 
 wherein said annular oil chamber is in fluid communication with said bearing surface oil passage for communicating said oil thereto. 
 
     
     
       9. A camshaft phaser as in  claim 8  further comprising a filter disposed within said annular oil chamber for substantially preventing particulate matter from entering said bearing surface oil passage and said harmonic drive oil passage. 
     
     
       10. A camshaft phaser as in  claim 1  further comprising:
 a coupling adapter attached coaxially to said wave generator and said rotational actuator for transmitting rotary motion from said rotational actuator to said wave generator; and 
 a bearing supporting said coupling adapter; 
 wherein said harmonic drive oil passage is in fluid communication with said bearing for supplying said oil thereto.